Check if input is a list/tuple of strings or a single string

Question

I've a method that I want to be able to accept either a single string (a path, but not necessarily one that exists on the machine running the code) or a list/tuple of strings.

Given that strings act as lists of characters, how do I tell which the method has received?

I'd like to be able to accept either standard or unicode strings for a single entry, and either lists or tuples for multiple, so isinstance doesn't seem to be the answer unless I'm missing a clever trick with it (like taking advantage of common ancestor classes?).

Python version is 2.5

Answer 1

Have you considered varargs syntax? I'm not really sure if this is what you're asking, but would something like this question be along your lines?

Answer 2

You can use type function

>>> type('/dev/null')
<type 'str'>
>>> type(['/dev', '/null'])
<type 'list'>
>>> type('/dev/null') is str
True
>>> type(['/dev', '/null']) is str
False
>>> type('/dev/null') is list
False
>>> type(['/dev', '/null']) is list
True

Answer 3

You can check if a variable is a string or unicode string with

isinstance(some_object, basestring)

This will return True for both strings and unicode strings

Edit:

You could do something like this:

if isinstance(some_object, basestring):
    ...
elif all(isinstance(item, basestring) for item in some_object): # check iterable for stringness of all items. Will raise TypeError if some_object is not iterable
    ...
else:
    raise TypeError # or something along that line

Stringness is probably not a word, but I hope you get the idea

Answer 4

Check the type with isinstance(arg, basestring)

Answer 5

Type checking:

def func(arg):
    if not isinstance(arg, (list, tuple)):
        arg = [arg]
    # process

func('abc')
func(['abc', '123'])

Varargs:

def func(*arg):
    # process

func('abc')
func('abc', '123')
func(*['abc', '123'])

Answer 6

isinstance is an option:

In [2]: isinstance("a", str)
Out[2]: True

In [3]: isinstance([], str)
Out[3]: False

In [4]: isinstance([], list)
Out[4]: True

In [5]: isinstance("", list)
Out[5]: False